#5458: fix: set correct file ownership in Dockerfile (#5450)

## Description This PR fixes a permission issue in the Docker environment where the `node` user was unable to access files owned by `root`. In certain environments (especially Linux/Ubuntu), the Docker engine copies files as `root` by default. Since the application runs as the `node` user, this lead to `EACCES: permission denied` errors when scanning the `extensions` directory, even though the files were present. (To be precise, permission issues occur with all files. It just happened to error out at the extensions first.) ## Changes - Added `--chown=node:node` to the `COPY` instruction in the `Dockerfile`. ## Related Issues - Fixes #5450 ## Testing - Verified on Ubuntu 22.04. - Confirmed that the "plugin not found" error no longer occurs during the onboarding process and plugins are loaded correctly. <!-- greptile_comment --> <h2>Greptile Overview</h2> <h3>Greptile Summary</h3> This PR updates the Docker build to copy the repository contents into the image with `node:node` ownership to prevent runtime `EACCES` errors when the container runs as the non-root `node` user (notably affecting `extensions/` scanning in some Docker/Linux setups). The change fits into the existing Docker hardening approach at the bottom of the `Dockerfile` where the container explicitly switches to `USER node` for runtime safety; ensuring files are owned/readable by that user avoids permission issues during onboarding/plugin loading. <h3>Confidence Score: 3/5</h3> - Mostly safe to merge, but broad ownership changes may cause avoidable build/runtime permission edge cases. - The change is small and addresses a real permission problem, but applying `--chown` to the entire context can unexpectedly alter permissions/ownership for generated artifacts and dependency trees, increasing the chance of subtle issues and rebuild churn. Limiting chown scope would reduce that risk. - Dockerfile <!-- greptile_other_comments_section --> _{(2/5) Greptile learns from your feedback when you react with thumbs up/down!} <!-- /greptile_comment -->